Hardening photographic gelatin and emulsion layers



Sept. 5, 1939. c. J. STAUD ET AL 2,172,300

HARDENING PHOTOGRAPHIC GELATIN AND EMULSION LAYERS Filed March 23, 1938 FIG. I.

I I GELA T/NO-S/L v51? HAL/DE EMULSION Wfiffilifilfiiififiifi HARDENED WITH AN AL/PHAT/C m ALDEHYDE ACE TAL suPPom;

HARDENED FILTER 'OR INTERLAYLI? EMULSION SUPPORT HARDENED AN Tl-HALA T/ON LA YER I7 'JIIIIII'IIII'IIIIIII'IIII C .YRIL J. STAUD GRAFTON H. KEYE5 INVENTORS BY MJMa? ATTORNEY 8 Patented Sept; 5, 1939 UNITED. STATES PATENT OFFICE HARDENING PHOTOGRAPHIO GELAT'IN AND EMULSION LAYERS Application March 23, 1938, Serial No. 197,684

14 Claims.

This invention relates to hardening photographic gelatin layers and particularly to hardening photographicgelatin emulsions. A

The photographic emulsions usually employed are known to be relatively sensitive to change in hydrogen ion concentration. Most emulsions have a pH slightly greater than 7, and if the pH of these emulsions is reduced materially below '7, a decrease in sensitivity of the emulsion results.

Many hardening agents used in photographic emulsions or gelatin solutions, particularly those containing carboxyl groups, tend to reduce the pH of the emulsion to such an extent that it is advisable, if not necessary, to adjust the pH of the hardening agent solution or of the emulsion so that the sensitivity of the emulsion is not impaired. It is frequently inconvenient to control the pH of an emulsion in this way and itis, therefore, .desirable to use a hardening agent which does not necessitate the use of these additional control agents.

It is, accordingly, an object of the present invention to provide a group of hardening agents which permit the processing of photographic emulsions at high temperatures. A still further object is to provide novel and satisfactory hardening agents for photographic emulsion, backing, and anti-halation layers. Other objects will appear from the following description of our invention.

These objects are accomplished by incorporating in photographic gelatin or emulsions an acetal of an aliphatic aldehyde.

In the accompanying drawing Fig. l is a sectional view of a film having a hardened emulsion layer, according to our invention, and Fig. 2 is a sectional view of a multi-layer film having hardened filter and anti-halation layers, according to our invention.

The photographic gelatin or emulsion layers are hardened according to our invention by mixing with a solution of the gelatin or emulsion, one of the hardening agents which we propose to use, dissolved in a suitable solvent which does not adversely affect the sensitivity of the photographic emulsion, in case the gelatin is to be used in the production of a sensitive layer.

The hardening agents which we use are acetals of aliphatic aldehydes such as p-ethoxyacrolein, glyoxal and acetylene dialdehyde. The

acetals produced from these aldehydes by reaction with alcohol are compounds such as p-ethoxyacrolein acetal, glyoxal tetramethyl acetal, glyoxal tetraethyl acetal and acetylene dialdehyde tetramethyl acetal. Other aliphatic a1- dehydes may be used and higher alcohols may be used to produce higher acetals from them. The specific compounds referred to above have the following structural formulae:

CZHlO-C H=C H fl-ethoxyacrolein acetal OCH:

O C H:

O CH: 15

O C H:

Glyoxal tetramethyl acetal Glyoxal tetraethyl acetal 30 O CH:

OCH:

OCH:

Aoetylene dialdehyde tetramethyl acetal The synthesis of p-ethoxyacrolein acetal is de- 40 scribed 'in Claesin and Ruder, Ber., 36, 8664 (1903).

In addition to their use in photographic emulsions, these compounds may also be used for the purpose of hardening gelatin used for filter lay- 45 .which has been subjected to the hardening action of an aliphatic acetaldehyde acetal. according to our invention. The subbing layers, antihalation layers etc. which are ordinarily present 5 in film are omitted from this figure for the of clarity.

Fig. 2 is a section view of a film in which the support II is coated with three superposed emulsions layers I8, I, and I! as is usual in some types of multi-color photography. A gelatin layer It is coated between the emulsion layers It and ll, the gelatin layer It being hardened with an aliphatic acetal, according to our invention. The layer It may serve either as an interlayer or it may contain a dye or coloring material so that it serves as filter layer. 0n the opposite side of the support ll there is coated an antihalation layer ll of gelatin containing an allphatic aldehyde acetal and a'dye or coloring material removable in the processing solutions, so

that it serves as an antl-halation layer.

We will not describe several specific embodiments of our invention, it being understood that these are illustrative only and are not to be considered the only methods of applying our invention.

Example I To about 10 cc. of ethanol there was added .015 gram of p-ethoxyacrolein'acetal to form a solution of the hardening agent. This solution was added to 225 grams (about 215 cc.) of a high speed photographic emulsion containing about 7% by weight of gelatin. After mixing the solution of the hardening agent with the emulsion the .mixture was immediately coated on a subbed cellulose acetate support and permitted to dry.

This layer was incubated for about two weeks at 113 F. and was then processed at a temperature of 85 F. The emulsion was unaflected by development, rinsing, fixing and washing at this temperature and did not melt or soften. The

control to which no hardening agent had been added was definitely softened by processing at this temperature.

Example I! To about 10 cc. of methanol there was added 0.2 gram of p-ethoxyacrolein acetal to form a solution of the acetal in methanol. This solution 0 was added to 210 grams (200 cc.) of a high speed photographic emulsion containing about 7% by weight of the gelatin. After mixing the solution of hardening agent with the emulsion, the emu sion was coated on a subbed cellulose acetate support. After incubation for about two weeks at 113 F. the film was processed in the usual way except that the processing solutions were maintained at 85 F. The emulsion was not melted or softened by processing in this way and,

although a similar film did show softening by processing-at 100 F., it did not melt by processing in that way as did a control sample.

Example III after exposure and processing at 1". it was found that the gelatin layer had not melted or softened appreciably. This type layer could be 7 satisfactorily used'as a backing layer to prevent abrasion or, if a suitable dye were added to it, to prevent halation.

Example IV 'and an anti-halation dyein a gelatin solution in the following proportions:

Grams 5% gelatin solution 200 10 Glyoxal tetraethyl acetal .1 Malachite green antihalation dye 2 This solution was coated on the back of an emulsion-coated support and permitted to dry. It was found to present a hard and durable surus face when the film was processed at high temperatures.

Although we have referred to specific conditions and proportions in the above example, it is to be understood that We are not limited to 20 the amounts specified. In certain cases the gelatin layers can be hardened by additionalamounts of these agents so that they can with stand temperatures as high as F. without melting. The emulsions may be treated at pHs' 25 between 6.5 and 8.5 and the hardening agents used according to our invention do not alter the pH nor afiect the sensitivity of. the' emulsion. Varying amounts of hardening agents may be used in both the emulsion and gelatin solutions. 80 In the emulsions the proportion of hardening agent may vary between about .l% and .5% of the weight of the emulsion and in the case of. gelatin solutions for backing or interlayers the. amount of hardening agent may extend up to as about 3% of the weight of a 5% gelatin solution. These amounts, however, are only approximate and it is to be understood that greater or lesser amounts of hardening agent may be used,

according to the requirements of the particular 40- type of photographic layer.

The aliphatic acetal used according to our invention may be incorporated in the gelatin or emulsions in various solvents, such as water, ethyl alcohol, methyl alcohol, ethyl acetate, 46 pyridine, molten acetamide, and others. Anysuitable solvent which does not impair the sensi-- tivity or otherwise adversely affect its photographic properties may be used in the case ofhardening agents intended for emulsion manu- 50 iacture. Numerous other modifications and equivalents of our invention are possible and our invention is to be taken as limited only by the scope of the appended claims.

What we claim is: 56

1. A gelatin layer containing as a hardening agent an acetal of an aliphatic aldehyde.

2. A gelatino-silver halide emulsion layer containing as a hardening agent an acetal of an aliphatic aldehyde. a0

3. A gelatino-silver halide emulsion layer containing as a hardening agent a glyoxal tetraalkyl acetal.

4. A gelatino-silver halide emulsion layer containing as a hardening agent glyoxal tetraas methyl acetal. Y

5. A gelatino-silver halide emulsion layer containing as a hardening agent fl-ethoxyacrolein acetal.

6. A gelatino-silver halide emulsion layer con- 70 taining as a hardening agent acetylene dialdehyde tetramethyl acetal.

7. The method of hardening photographic gelatin which comprises incorporating therein an acetal of an aliphatic aldehyde. v 1|,

8. The process of producing a hardened gelatino-silver halide emulsion layer which comprises adding a solution of an acetal of an aliphatic aldehyde to a melted emulsion, and then coating the emulsion on a rigid support.

9. The process of producinga hardened gelatino-silver halide emulsion layer which comprises adding a solution of an acetal of an aliphatic aldehyde to a melted emulsion, the amount of acetal being about 0.1% to about 0.5% of the weight of the emulsion, and then coating the emulsion on a rigid support.

10. The process of producing a hardened gelatino-silver halide emulsion layer which comprises adding a solution of an acetal of an aliphatic aldehyde to a melted emulsion, the amount of acetal being about 0.1% of the weight of the emulsion, and then coating the emulsion on a rigid support.

11. A composition of matter comprising a solution of gelatin containing as a hardening agent,

an acetal of an aliphatic aldehyde.

12. A-composition of matter comprising a solution of gelatin containing p-ethoxyacrolein acetal as a hardening agent.

13. A composition of matter comprising a solution of gelatin containing as a hardening agent, a glyoxal tetraalkyl acetal.

14. A composition of matter comprising a 5% solution of gelatin containing as a hardening agent, about 0.1%, based on the weight of the, solution, of an acetal of an aliphatic aldehyde.

CYRIL J. STAUD. GRAFTON H. KEYES. 

